Package org.apache.lucene.search

Class IndriDisjunctionScorer

java.lang.Object

org.apache.lucene.search.Scorable

org.apache.lucene.search.Scorer

org.apache.lucene.search.IndriScorer

org.apache.lucene.search.IndriDisjunctionScorer

Direct Known Subclasses:

IndriAndScorer

public abstract class IndriDisjunctionScorer
extends IndriScorer

The Indri implemenation of a disjunction scorer which stores the subscorers for the child queries. The score and smoothingScore methods use the list of all subscorers and not just the matches so that a smoothingScore can be calculated if there is not an exact match.

Nested Class Summary

Nested classes/interfaces inherited from class org.apache.lucene.search.Scorable

Scorable.ChildScorable

Field Summary

Fields inherited from class org.apache.lucene.search.Scorer

weight

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	IndriDisjunctionScorer(Weight weight, List<Scorer> subScorersList, ScoreMode scoreMode, float boost)

Method Summary

Modifier and Type	Method	Description
int	docID()	Returns the doc ID that is currently being scored.
float	getMaxScore(int upTo)	Return the maximum score that documents between the last target that this iterator was shallow-advanced to included and upTo included.
List<Scorer>	getSubMatches()
DocIdSetIterator	iterator()	Return a DocIdSetIterator over matching documents.
float	score()	Returns the score of the current document matching the query.
float	smoothingScore(int docId)	Returns the smoothing score of the current document matching the query.
abstract float	smoothingScore(List<Scorer> subScorers, int docId)

Methods inherited from class org.apache.lucene.search.IndriScorer

getBoost

Methods inherited from class org.apache.lucene.search.Scorer

advanceShallow, getWeight, twoPhaseIterator

Methods inherited from class org.apache.lucene.search.Scorable

getChildren, setMinCompetitiveScore

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

IndriDisjunctionScorer

protected IndriDisjunctionScorer(Weight weight,
                                 List<Scorer> subScorersList,
                                 ScoreMode scoreMode,
                                 float boost)

Method Detail

iterator

public DocIdSetIterator iterator()

Description copied from class: Scorer

Return a DocIdSetIterator over matching documents.

The returned iterator will either be positioned on -1 if no documents have been scored yet, DocIdSetIterator.NO_MORE_DOCS if all documents have been scored already, or the last document id that has been scored otherwise.

The returned iterator is a view: calling this method several times will return iterators that have the same state.

Specified by:

iterator in class IndriScorer

getMaxScore

public float getMaxScore(int upTo)
                  throws IOException

Description copied from class: Scorer

Return the maximum score that documents between the last target that this iterator was shallow-advanced to included and upTo included.

Specified by:

getMaxScore in class IndriScorer

Throws:

IOException

getSubMatches

public List<Scorer> getSubMatches()
                           throws IOException

Throws:

IOException

smoothingScore

public abstract float smoothingScore(List<Scorer> subScorers,
                                     int docId)
                              throws IOException

Throws:

IOException

score

public float score()
            throws IOException

Description copied from class: Scorable

Returns the score of the current document matching the query.

Specified by:

score in class IndriScorer

Throws:

IOException

smoothingScore

public float smoothingScore(int docId)
                     throws IOException

Description copied from class: Scorable

Returns the smoothing score of the current document matching the query. This score is used when the query/term does not appear in the document, and behaves like an idf. The smoothing score is particularly important when the Scorer returns a product of probabilities so that the document score does not go to zero when one probability is zero. This can return 0 or a smoothing score.

Smoothing scores are described in many papers, including: Metzler, D. and Croft, W. B. , "Combining the Language Model and Inference Network Approaches to Retrieval," Information Processing and Management Special Issue on Bayesian Networks and Information Retrieval, 40(5), pp.735-750.

Specified by:

smoothingScore in class IndriScorer

Throws:

IOException

docID

public int docID()

Description copied from class: Scorable

Returns the doc ID that is currently being scored.

Specified by:

docID in class IndriScorer